#include <bits/stdc++.h>
using namespace std;
long long arr[1000050],n,m,ans=-1,maxx=0;
bool check(int x){
	long long sum=0;
	for(int i=1;i<=n;i++){
		if(x<arr[i]){
			sum+=arr[i]-x;
		}
	}
	return sum>=m;
}
int main(){
	cin>>n>>m;
	for(int i=1;i<=n;i++){
		cin>>arr[i];
		maxx=max(maxx,arr[i]);
	}
	long long l=0,r=maxx;
	while(l<=r){
		int mid=(l+r)/2;
		if(check(mid)){
			ans=mid;
			l=mid+1;
		}else{
			r=mid-1;
		}
	}
	cout<<ans;
	return 0;
}

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NSAyMAo0IDQyIDQwIDI2IDQ2

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